Pebble grinding-mill.



H. D. McLEOD.

PEBBLE GRINDING MILL.

APPLICATION FILED JULY 2,1903

Patented Sept. 8, 19M

FIG 1 'HOWARD D. MULEOD, OF CLEVELAND HEIGHTS, QHIO.

EEBBLE GRINDING-MILL.

Specification of Letters Patent.

Patented Sept, 8, HEM.

Application filed. July 2, 1908. Serial No. 441,555.

To all whom it may concern:

Be it known that I, HOWARD D. MoLnoo,

a citizen of the United States, residing at.

Cleveland Heights, in the county of Guyahoga and State of Ohio, have invented a certain new and useful Improvement in Pebble Grinding-Mills, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings.

This invention relates to grinding mills of the type known as pebble mills, wherein pebbles, or balls, or other materials are employed for the purpose of grinding wet or dry material. A large field of usefulness for mills of this character resides in the grinding of ore, to reduce the particles to pulverulent condition before recovering metals therefrom, although such mills may be used for grinding other materials, as cement, for instance. Mills of this kind, as hertoiore constructed, have been generally cylindrical in form and provided at opposite ends with trunnions on which they are supported. These trunnions are hollow to constitute respectively a feed inlet and a discharge outlet for the material to be ground. All mills of this type with which 1 am familiar have been arranged substantially horizontally, any inclination of the axis being very slight.

It is the purpose of my invention to pro vide a mill of this character which will produce a continuous series sizing of the mate rial from the inlet to the discharge outlet, which will effect the grinding or pulverizing with great rapidity, which will secure constancy in the sizing of the material, and which will generally be of increased Q13; ciency over mills which have been hereto fore constructed. 1 accomplish these results by the forms of my invention illustrated in the drawings forming a part hereof, where1n- Figure 1 represents a central vertical longitudinal sectional view taken through a mill constructed in accordance with my in-' vention, certain parts being shown in elevation; Fig. 2 represents a detail of the mechanism for rotatin the mill shown in the preceding figure; lFig. 3 represents a side elevation of a modification of the invention Shown in Fig. 1; Fig. 4 represents a similar view or" another modification of the invention shown in Fig. 1; and Fig. 5 represents a diagrammatic side elevation of the form of my invention shown in Fig. 1 wherein the axis of rotation is arranged eccentrically with respect to the longitudinal axis of one of the members of the mill.

Describing the parts by reference characters, particular reference being made to Fig. 1, 1 denotes the body of the mill. This body comprises an outer metallic shell 2, which is preferably of steel plate, having therein a suitable lining 3. The body of the mill is composed of a plurality of frusto-conical members having the smaller end or base of one connected to and communicating with the larger end or base of the other. Two such members are shown, the shell of one member being connected with the shell of the other by means of a heavy cast steel plate a, to which the lining 3 is applied. For convenience or description, the contracted end of the larger member, through which the feed is introduced, will be referred to hereinafter as the front end and the enlarged end of the smaller memher will be referred to as the rear end of the mill. The large or rear end of the smaller member is provided with a plate 5, similar to plate 4:, to the rear end of which there is attached the hollow trunnion 6. This trunnion constitutes the discharge outlet for the mill and is mounted in a suitable bearing 7 supported by a standard 8. 9 denotes a trough into which the trunnion .6 discharges.

The front member of the mill is provided intermediate between the ends thereof with a beveled rack 10 meshing with beveled gears 11 and 12. These gears are supported on opposite sides of a central drive pinion 13, which is mounted on a shaft 14 to which a pulley 15 is applied. llhe shafts of gears 11 and 12 will be preferably supported between a pair of standards 16, through which the shaft 14 also extends and will be arranged at such angle with respect to shaft 14 as will enable them to mesh with the rack 10. Pinion 13 meshes with both of the bevel gears and drives the same and thereby rotates the mill. The rack is provided with a solid rim 10 adapted to rest upon solid portions 11 and 12 of gears 11 and 12 to carry the weight of the front end of the mill while it is being rotated by the gears.

As will appear from Fig. 1, the mill is inclined at a considerable angle with respect to the horizontal, this angle being shown as about 15 degrees.

In operation, the pebbles or grinding balls (indicated at 17), are introduced into the mill and occupy approximately the positions shown in the drawing. The material to be ground is introduced into the front end of the larger member of the mill through a suitable chute or spout 18. Owing to the inclination and construction of the mill, this material (indicated at 19) as the mill is rotated is subjected to a series classification. The coarser portions of this material will be at the inlet or front end of the mill. As this material travels from the front to the rear end of the mill it is subjected to a progressive grinding, both by the contact of the particles of material with each other and the contact of the material with the pebbles 17. There is a natural tendency for the finer material to seek the rear and deeper portions of the mill, which is where the pebbles naturally accumulate. The step formed between the two members of the mill by the base or bottom of the first member forms a retaining wall for the pebbles in this member and maintains these pebbles separate from those in the other or smaller member. The sloping bottoms of the two members of the mill tend to pocket the pebbles and to provide for the series classification referred to. With the construction of mill described, a great saving in length of mill may be accomplished and the crushing or grinding may be accomplished with the use of a much smaller amount of pebbles than has heretofore been considered necessary for this work. Fur thermore, by the inclination given to the mill, the material is fed therethrough more quickly than is the case with other constructions with which I am familiar, and the necessity for a power-driven feed device is obviated. Furthermore, a more rapid sizearrangement or classification of the particles is produced since, as soon as the material is crushed in any one zone it automatically shifts its position another step toward the discharge end of the mill and into a zone of finer crushed materials, pebbles or balls. Thus the coarser pebbles or balls are freed from the congesting action which is inevi-- table in other mills of this character with which I am familiar.

In Fig. 3 there is shown a modification of my invention wherein the two members .20 and 21 of my mill are represented as cylindrieal bodies of different diameters, the body of smaller diameter being at the rear of the one of larger diameter and being connected to the end of the latter in the same manner as the connection is formed between the two members of the mill shown in Fig. 1. In both cases, the axes of the mill are inclined at a considerable angle and the two members are separated by a step. Member 20 is provided with a circular rack 10* by means of which the mill shown in Fig. 3 may be rotated in the same manner as that shown in Fig. 1.

In Fig. 4 of the drawing there is shown a modification of the invention shown in Fig. 1, wherein both ends of the mill are provided with hollow trunnions 6 and 6". The former trunnion is supported by a suitable frame or standard 8 and the latter by a suitable frame or standard 22. The trunnion 6 is provided with a beveled rack 23 which is driven in the same manner as the racks 10 and 10 The feed is introduced into the mill shown in Fig. 4 by means of a spout 24 entering the hollow trunnion 6".

In Fig. 5 there is shown a still further modification of my invention wherein the two members of the mill 20 21 are shown as frusto-conical members (as in Fig. 1) but with the rear member connected eccentrically to the front member and the rear memher having at its rear end a hollow trunnion 25, the center whereof coincides with the axis of the front member, said axis being indicated by the line a2-a2 and the axis of the rear member being represented by the line y y. The front and rear of the mill shown in Fig. 5 may be supported and driven in the same manner as the fronts of the mills shown in Figs. 1 and 8. By this construction, material ground in the front member is intermittently discharged into the rear member whenever that portion of the flange on the front member which is of least width is at or near the bottom of the mill. While the form of my invention shown in Fig. 5 produces a series sizing from front to rear, this action is modified at the junction of the two members, where a bodily dislodgment of the .material occurs, which facilirates the travel of the material from one member to the other and increases the crushing action.

ltlaving thus described my invention, it claim:

l. A grinding mill having a rotary body formed of a plurality of connected members, one of said members having its axis eccentric with respect to the longitudinal axis of said body, and means for rotating said body.

2. A grinding mill having an inclined rotary body. said body comprising a pair of members. the front member being provided with an inwardly directed flange at its rear 1,110,0ee i end and the rear meniber being connected In testimony whereof, I hereunto afiix to the inner periphery of said flange and my signature in the presence of two Wii;- 10 being provided at its rear end with an inne$es.

Wardly projecting flange having a discharge outlet, the axis of rotation of said body be- HUWARD MCLEOD' ing eccentric With respect to the axis of the Witnesses:

rear member, andmeans for rotating said J. B. HULL,

body. 1 BRENNAN B. WEST, 

